A pad pitch of a semiconductor chip that becomes rapidly finer and a pad pitch of a board (mount board) on which the semiconductor chip is mounted are different by more than an order of magnitude. This makes it difficult to reflect performance of a high performance and high functional chip obtained by progress in the semiconductor technology on a device or a system.
For example, a pad pitch of a practically usable semiconductor chip becomes 50 μm or less. In contrast, a pad pitch of a mount board (for example, printed board) is about 500 μm. It is estimated that the pad pitch of the semiconductor chip becomes finer in the coming years along with a scaling rule. However, it is believed that a development of the mount board having a fine pad pitch is relatively slow.
An interposer is to convert correspondingly a wiring pitch between the narrow pad pitch of the semiconductor chip and the wide pad pitch of the mount board, and is generally a silicon interposer using silicon. However, the silicon interposer is very expensive in terms of a material, and is also very expensive in terms of a process that needs an apparatus and a technique for preprocess.
Here, Patent Literatures 1 and 2 each discloses a technique that a build-up wiring board formed by multi-layering fine-pitch wiring corresponding to specifications of the silicon interposer is used in combination, and the silicon interposer and the build-up wiring board are resin-molded together.